Apple has since pulled the update, issuing an apology and posting instructions for users to restore their iPhones to the original iOS 8 software.
In a post on the Apple support page, the company says: "We have a workaround for iPhone 6 and iPhone 6 Plus users who lost cellular service and Touch ID functionality today after updating to iOS 8.0.1. Affected users can reinstall iOS 8 through iTunes, for more information visit http://support.apple.com/kb/HT6487.
"We apologise for the great inconvenience experienced by users, and are working around the clock to prepare iOS 8.0.2 with a fix for the issue, and will release it as soon as it is ready in the next few days."
iOS 8.0.1 was released to correct a bug with the original iOS 8 software which affected health and fitness apps on the new Apple HealthKit platform. Unfortunately, this fix has clearly had a knock-on effect on core iPhone functionality.
More after the break
The software issue comes as some iPhone 6 Plus users are reporting that the new Apple phablet is susceptible to bending. Videos surfaced of the iPhone 6 Plus bending (see above), while other users reported their phones had bent just from being in their pockets, with '#bendgate' soon trending worldwide on Twitter.
We're putting our iPhone 6 Plus through its paces now and will be publishing our in-depth review very soon, but it's fair to say that our model, while it will bend under severe pressure, doesn't seem to flex any more than some rival big-screen handsets.
Apple had previously heralded its "best launch ever", having sold 10 million iPhone 6 phones over the launch weekend, but the iOS 8 issues saw Apple's shares drop to 101.75, down 0.9 per cent, on Wednesday. That share price is up 45 per cent on this time last year, however.
Have you got an iPhone 6 or 6 Plus? Have you experienced any problems? Let us know by leaving a comment below.
UPDATE: Apple has today (Friday, 26th September) released the iOS 8.0.2 update, which claims to fix all the above problems (apart from any bending...).